The term gel must be understood as describing the physical state of the final product. The terms polyurethane gel therefore refer at present to a plasticized polyurethane obtained by bringing a plasticized composition (I) based on at least one polyol into contact with at least one polyisocyanate.
For certain highly specific electrical applications such as electrical insulation or cable filling, or else for paramedical applications (antiscab mats and pads, mammary prosthesis), polyurethane gels are required which have a low consistency and which are obtained rapidly after the composition (I) has been brought into contact with a polyisocyanate.
More precisely, what is sought after is plasticized compositions (I) based on polyols which, at ambient temperature (approximately 20.degree. C.) have a high viscosity, equal to or higher than 4 Pa.cndot.s and in which the reactants (polyols) are capable of reacting with the polyisocyanate.
Known plasticized compositions contain high plasticizer ratios which are likely to lower considerably the viscosity of the said polyol-based compositions.
Thus, U.S. Pat. No. 4,787,905 describes a gel which can be employed for the manufacture of a mammary prosthesis. A low-viscosity plasticized composition is produced for this purpose, containing 10% by weight of a polydiene polyol and 90% by weight of undecyl phthalate.
Similarly U.S. Pat. No. 4,666,968 describes a low-viscosity polyurethane gel which can be employed in electrical insulation and which contains a high plasticizer content. This gel is obtained particularly by bringing a plasticized composition containing a polyisocyanate into contact with a highly plasticized composition containing polyols.
U.S. Pat. No. 5,258,578 also describes low-viscosity polyurethane gels which can be employed for cable terminals and connection boxes.